Saturday, 26 May 2012

6 June 2012 will be the last Transit of
Venus this century, and it’s visible from the southern hemisphere. Yes,
Veronica, you too can be just like Captain Cook! Well, not quite. But it’s very
exciting to me that in our lifetimes Venus will cross the face of the Sun just
as it did in Cook’s day. It was, of course, the observing of the transit which
was the immediate, possibly one should say ostensible, reason for the British
Government’s dispatching Cook to the South Seas.

It will be daylight on 6 June in the
Southern Hemisphere when Venus crosses the Sun. The best view in Australia will
be from the eastern states. The Transit will be visible in the morning from
Adelaide, optimum time about 11 a.m. The website below will be providing full
video coverage, so if viewing from where you are isn’t good, why not try to
catch it online? And DON’T look at it with the naked eye!!

http://www.transitofvenus.com.au/HOME.html
: This site is clear, easy to follow and very informative. Its downloadable PDF
tells us: “Transits of Venus occur in a pattern that repeats every 243 years
with pairs of transits eight years apart separated by gaps of 121 1/2 years and
105 1/2 years.” The next isn't due until
2117.

There are lots of other online sites with
information about the history of the transits, more or less baffling to those
with unscientific minds! However, for a very readable introduction to the topic,
with lots of wonderful illustrations from the contemporary documents and of the
contemporary instruments, you can't go past this publication from Sydney’s Powerhouse
Museum:

What made
this book more interesting for me was that many of the illustrations are taken
from Australian sources - not just items from the Powerhouse itself, but also
from other institutions, such as the National Library of Australia and the
Mitchell Library in Sydney, which both hold marvellous and unique manuscripts
and pictures.

I won’t attempt to give you the full story
of the Transit of Venus, it’s been told by experts, which I’m certainly not.
What I’d like to do here is just highlight some of the fascinating facts I came
across when reading up about the 1769 transit and its relation to Cook, and
tell you about some of the related materials held by the Royal Geographical
Society of South Australia (online catalogue: http://rgssa.slimlib.com.au:81/vufind/ )

Why the Transit of Venus?

So what exactly was it about the transit?
Why was Cook sent out to observe it? I won’t go into the astronomy of it,
because frankly it’s beyond me! But I have read the relevant chapter in J.C. Beaglehole’s
The
Life of Captain James Cook (London : Hakluyt Society, 1974), which
forms volume IV of his definitive ed. of the Journals, as well as Lomb’s book. Taking observations of the
transit from as many positions as possible round the world would allow astronomers
to measure the correct distance of the Sun from the Earth. It was the Royal Society
which prodded the British Government into action, making the point that
foreigners were going to make us British look small if we didn’t get off our
butts and send some observers out, by Jove! Much more politely, of course. But
there was also the point that these foreigners were out there in the South
Seas, which would be a jolly good place for Britain to expand her empire and her
trade interests. Especially as it was still believed that a great southern
continent lay down there. Gee, it had to, to balance the land mass of the
northern hemisphere!

The Great Southern Land: Balancing the Land Mass
of the Northern

Hemisphere

No, true: this idea goes back to Ptolemy.
No? Well, I'd heard the name, but until recently didn't know a thing about him.
You can look him up in the RGSSA’s online catalogue: you’ll find he's listed as
“Ptolemy, 2nd cent.” Here are some quick facts from the Encarta:

“Ptolemy
(c. 100-c. 170), astronomer and mathematician, whose astronomical theories and
explanations dominated scientific thought until the 16th century (... Ptolemaic
System). He is also remembered for his contributions to the fields of
mathematics, optics, and geography. Ptolemy was probably born in Greece, but
his actual name, Claudius Ptolemaeus, reflects all that is really known of him:
“Ptolemaeus” indicates that he was a resident of Egypt, and “Claudius”
signifies Roman citizenship. In fact, ancient sources report that he lived and
worked in Alexandria, in Egypt, for most of his life.

“...Of
considerable historic importance is Ptolemy's Geography, which charts the world as people of his time knew it.
This work, which employs a system of latitude and longitude, influenced
map-makers for hundreds of years, but it suffered from a lack of reliable
information.” -Microsoft Encarta 2006.

Er, yes. The Encarta puts it temperately, but the fact is, “suffered from a lack
of reliable information” plays it down to a positively ludicrous extent! On
Ptolemy’s map of the world the whole of the southern hemisphere is a work of
the imagination: there’s a sea, sort of equal to the Indian Ocean, and below
it, an enormous land mass in which Africa is joined to something more southerly
which stretches the width of the globe.

One of the Mediaeval depictions of Ptolemy's description of the whole inhabited world,
which shaped beliefs about the southern continent: a printed map form the 15th
century (1482, Johannes Schnitzer, engraver)

This wouldn’t have mattered if it had stayed
stuck in the second century A.D., but alas, just when printing had been
discovered, the work was published in a Latin translation. That did it. This
was the definitive version. It was of course backed up by all sorts of theories,
terrifically well thought out, but based on nothing but imagination. Gradually
the discoveries of the Portuguese, Spanish and Dutch began to put paid to some
of the misconceptions, but by Cook’s time, sixteen
centuries after Ptolemy, the idea of a huge southern continent was still
very much a reality - amazingly, it may well seem to us, less than two and a
half centuries later.

You’d like something even more amazing?
Well, here it is! Those early printed books are, very rare and very valuable,
and guess what? The Royal Geographical Society of South Australia has actually
got a copy of Ptolemy’s Geographia!:

Photograph of the inhabited map of the world in RGSSA's copy of
Ptolemy's Geographia

Well, no, you can't actually walk in and
put your grubby mitts on it; it’s kept for us in the State Library of South
Australia’s Rare Books Room, i.e. the vault, locked. You’d need to make an appointment to see it. But it is
sometimes brought out on special occasions. I have seen it, it was out just
recently. It’s got quite a modern binding but the inside is the real thing. No,
I didn't put my sticky paws on it.
And the printed text isn't that exciting to look at it, I suppose, but it’s the
fact of its being there! Wow!

The contemporary state of knowledge of the
southern hemisphere in the 18th century is pretty well documented by the work
of De Brosses, well represented in the RGSSA collection. This is our French
edition:

“This
offers a complete digest of all known voyages to the Southern seas, preceded by
a long plea for an exploration campaign in these waters, in order to discover
and exploit the vast Austral continent which could not fail to be there, for
mechanical reasons. It proved extremely useful to James Cook with respect to
the discovery of Australia in 1770, and contains what may be the first
occurrence of the words "Polynésie" and "Australasie". It
has been written that it is this book which convinced the French explorer
Louis-Antoine de Bougainville, then a soldier in Canada, to become a sailor
and, in his own terms, ‘do something great’.” (Charles de Brosses, Wikipedia)

Portrait of Charles de Brosses (copper engraving) by Charles-Nicolas Cochin

And this is the RGSSA’s edition of the
English translation:

Brosses, Charles de,
1709-1777.

Terra Australis cognita: or,
voyages to the Terra Australis, or Southern Hemisphere, during the sixteenth,
seventeenth, and eighteenth centuries. Containing an account of the manners of
the people, and the productions of the countries, hitherto found in the Southern
latitudes; the advantages that may result from further discoveries on this
great continent, and the methods of establishing colonies there, to the
advantage of Great Britain. Edinburgh : printed for the author; and sold by Messrs.
Hawes, Clark, and Collins, London, 1766-68.
3 v.

I particularly like the last phrase of the
English edition’s title: “to the advantage of Great Britain”- not present in the French! It’s very
much indicative of the mood of the times. As Cook’s sealed orders were to
reveal, once he'd observed the transit, the real purpose of his expedition was
to sail further south and check out the southern latitudes for the fabled
southern continent on behalf of the British Government.

It's fascinating that Beaglehole tells us
in so many words that De Brosses was a disciple of Ptolemy: in his book he “traversed
the voyages in the southern hemisphere... Somewhere in those regions must be
civilisations that only waited to exchange the lessons of culture with France.
Could that whole unknown part of the globe be occupied by nought but the waters
of the sea? Capes, fragments of coast, were certain signs of a continent. Must
there not be, southwards of Asia, solid land extensive enough to counterweight
the northern mass, to maintain in equilibrium the whole rotating globe? It is
the classical argument; we see again the Ptolemaic sphere”. (The
life of Captain James Cook, p. 119)

Can you feel it? Can you feel how it all hangs together? Can you feel the
weight of history? I hope you can, dear blog reader. Because it's thrilling!
And it’s just astounding that here, down at the south of the great brown land
where we wouldn't even be speaking English if it hadn't been for the effort,
determination and genius of a country lad from the North Riding, we’ve got the
books where it's all documented for us.

Everything Aligned Just Right: From Halley’s
Instructions

to
Captain Wallis’s Discoveries

The Endeavour
voyage of 1769 came just at the right time: navigation had advanced to the point
where, if you used the method of “lunars” (lunar distances), you could
calculate your longitude, if you were a very, very good navigator. (Harrison’s
chronometer had been trialled successfully but it was hugely expensive and not
yet in general use and Cook didn't have one, though he was to use it for later
voyages.) The method Cook used on the Endeavour
trip was greatly helped by the publication by Nevil Maskelyne, the Astronomer
Royal, of the annual Nautical Almanac and
Astronomical Ephemeris “with tables listing the angular distances of bright
stars for the moon at different times” (Lomb, op. cit. p. 48). Then, Edmond Halley (the Halley’s comet astronomer,
who himself had observed a transit of Mercury) had set down very clear
instructions for observing a transit, some 50 years earlier. You had to view
both the beginning and end of the transit (“ingress”, when Venus first enters
across the face of the Sun, and “egress”, when it leaves). Later, a French
astronomer, Joseph-Nicolas Delisle, had devised a slightly different method, based
on Halley’s: this entailed observing either ingress or egress and timing the
process from different places round the earth. (Ibid, p. 50). Astronomers of the time would use a combination of
both methods, sending out observers to many places, from India to Baja
California as well as the Pacific, to record their observations.

Another very important factor in Cook’s
mission was the return of Captain Samuel Wallis of the Dolphin very shortly before Cook was due to leave England. Wallis
discovered Tahiti, naming it “King George’s Island”, and pinpointed its
latitude and longitude; and Tahiti just happened to be the right spot for
observing the Transit!

"The Natives of Otaheite Attacking Captain Wallis the First Discoverer of That Island":

Wallis's voyage is described in:

Hawkesworth, John, 1715?-1773.

An account of the voyages
undertaken by the order of His present Majesty, for making discoveries in the
southern hemisphere, and successively performed by Commodore Byron, Captain
Wallis, Captain Carteret, and Captain Cook, in the Dolphin, the Swallow, and
the Endeavour : drawn up from the journals which were kept by the several
commanders and from the papers of Joseph Banks, Esq. London : Printed for W.
Strahan and T. Cadell, 1773. 3 v.

And it’s commemorated by:

Fitz-Gerald, Gerald, 1739?-1819

The injured islanders, or, The
influence of art upon the happiness of nature. London : Printed for J. Murray,
1779. [5], 25, [2] p.

A poem,
purporting to be an address from “Oberea”, deposed queen of Tahiti, to Samuel
Wallis, deploring the effect his visit had on the native population. Its
authorship has been erroneously attributed to Wallis himself, but it is now
said to be by Fitz-Gerald.

So there was the method, the spot, and lo!
The British Admiralty just happened to be able to lay its hands on a very, very
good navigator - the obscure Mr James Cook. He was only a “master” at the time
- like a non-commissioned officer. In order for him to captain the ship he was
commissioned as a lieutenant, a huge step-up for a working-class country boy
from oop Yorkshire way.

And with the ship fully provisioned, including
the appropriate astronomical instruments, funded by a British Government grant
to the Royal Society, they set off for the great empty space of the deep blue
Pacific.

Cook & his Companions: the Voyage to Observe
the Transit of 1769

Well! The Royal Geographical Society of
South Australia’s got a pretty extensive collection of materials relating to
Cook’s first Pacific voyage, all right! Several editions of his journals,
including both the 1893 edition of W.J.L. Wharton’s Captain Cook's journal during his
first voyage round the world made in H.M. Bark "Endeavour", 1768-71 :
a literal transcription of the original mss (London: Elliot Stock), and
the 1968 facsimile reproduction of it (Adelaide: Libraries Board of South
Australia), plus the definitive edition edited by the New Zealand scholar, J.C.
Beaglehole:

Cook, James, 1728-1779

The Journals of Captain James
Cook on his voyages of discovery. Cambridge: Published for the
Hakluyt Society at the University Press, 1955-1974. 4 v.

Other works include the 7-volume The
three voyages of Captain James Cook round the world (Longman, Hurst,
Rees, Orme and Brown, 1821)

The Endeavour journal of Joseph
Banks : 1768-1771 / edited by J.C. Beaglehole. Sydney : The Trustees of the Public
Library of New South Wales in association with Angus and Robertson, 1962. 2 v.

We also hold two early editions of the young
artist Sydney Parkinson’s posthumously published journal, which include
reproductions of his sketches of the 1769 visit to Tahiti:

Parkinson, Sydney, 1745?-1771.

A journal of a voyage to the
South Seas, in His Majesty's ship, the Endeavour faithfully
transcribed from the papers of the late Sydney Parkinson ... : embellished with
views and designs, delineated by the Author, and engraved by capital artists. London : Printed
for Stanfield Parkinson, the editor: and sold by Messrs Richardson and
Urquhart..., 1773. [ii], xxiii, 212, [1] p., [27] leaves of plates

Parkinson, Sydney, 1745?-1771.

A journal of a
voyage to the South Seas in His Majesty's ship the Endeavour faithfully
transcribed from the papers of the late Sydney Parkinson ... . To which is now added, Remarks on the preface
by John Fothergill and an appendix containing an account of the voyages of
Commodore Byron, Captain Wallis, Captain Carteret, Monsieur Bougainville,
Captain Cook, and Captain Clerke. London : Printed for Charles Dilly ... and
James Phillips..., 1784. [2], xxiii, [1], 22, 212, lxxi p., [213]-353, [3] p.,
27 leaves of plates

"Venus Fort, Erected by the Endeavour's People to secure themselves during the Observation
of the Transit of Venus, at Otaheite" by Sydney Parkinson; Plate IV from "A Journal of a Voyage
to the South Seas, in His Majesty's Ship, the Endeavour": the engraving is from his sketch
done on the spot in 1769

Cook himself took the observations of the
Transit of Venus. He had one excellent telescope, and his assistant, a Mr
Green, an ex-employee at Greenwich, had another, made to exactly the same
specifications. As well, the scientist Daniel Solander, Banks's friend, had a
really good telescope of his own, which he used to observe and record. The 3
June 1769 was a lovely day, very clear, and very hot. As they had arrived in
plenty of time they had ample time to make proper preparations. They built a
little observatory to sit in with their telescopes (set up so as they could
observe the reflections, of course, not for looking through with the naked
eye). They also had a special astronomical clock which was housed separately,
set very firmly and solidly indeed. As a precaution, Cook sent off two back-up
parties to adjacent islands as well.

Diagram of the 1769 Transit of Venus showing where it could be seen from Earth.
Tahiti is at approximately the intersection of the two circles

Everything went splendidly - luck was
certainly with Cook at this time, though of course his careful preparations
were always crucial to his many successes. But they found to their disappointment
that because of a kind of hazy ring around the disc of Venus it was impossible
to get an accurate timing of ingress and egress. All three of them observed
this effect, which Cook called a “penumbra”: it is now a recognised phenomenon
but they were very upset, as they’d had no warning of it. Cook’s very own sketches
of it are in the manuscript of his journal held by the Mitchell Library, State
Library of New South Wales (photo in Lomb, op
cit, p. 90). Cook’s writing is faded but he must have used different ink
for sketching: the diagrams are small but you can see the penumbra very
clearly, and exactly how it blurs the actual point at which Venus touches the
edge of the sun.

After the Transit

Cook’s observations of the Transit of
Venus had been a success within the limits of the technology of the time even
though the three chief observers at Tahiti didn't feel they'd wholly succeeded.
Hundreds of calculations were presented to the Royal Society in the wake of the
1769 transit. There was quite a spread in the calculations of the distance from
Earth to the Sun but the variations were reduced by millions of K from the estimates
of the 1761 transit, the first ever observed. It wasn't to be until 1824 that
the German scientist, Encke, put the two transits’ calculations together and worked
out a distance of 153.3 million K, an estimate that was to stand for decades as
the “definitive value of the solar distance.” (Lomb, op. cit p. 104) Modern astronomy has worked out that it is in fact
less: 149.6 million K.

Sailing south as ordered, Cook verified
there was no fertile southern continent thereabouts, circumnavigated and mapped
New Zealand and, following his orders to go home either via the Cape of Good Hope or Cape Horn, opted for the former, as they’d
hit winter weather if they headed for the Horn. On the way, he decided, he'd
find and chart the eastern coast of “New Holland.”

So he did. He named the country “New South
Wales” and claimed it, as he had New Zealand, for the British Crown. And the rest
is history?

No, Veronica, that is history.

Before I sign off I must just say many
thanks to Sandra Thompson for alerting me to the fact that the 2012 Transit of
Venus is coming up and providing the helpful website address, and to Peggy
Molloy for finding the book by Lomb for me. I’ve had a fascinating time reading
up about it.